Serum/plasma thyrotropin (TSH) concentration
This test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH is a hormone produced by your pituitary gland that helps regulate thyroid function.
["TSH helps your thyroid produce hormones that control metabolism."]
Key facts at a glance
- LOINC
- 50534-7
- Short code
- TSH sp2 SerPl-aCnc
- Synonyms
- TSH sp2 SerPl-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.4
- Ref high
- 4
- Critical range
- 0.1 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84443
- SNOMED
- 301343003
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order a TSH test to check for thyroid problems, such as hypothyroidism (when your thyroid isn’t producing enough hormones) or hyperthyroidism (when it’s overactive). It’s often the first test for thyroid issues because it’s sensitive and easy to perform. TSH levels can also be checked during pregnancy, before surgery, or if you have symptoms like fatigue, weight changes, or unexplained mood swings.
What to Expect Before the Test
No special preparation is usually needed, but your doctor might ask you to fast for a few hours before the blood draw if you’re having it done in the morning. Wear comfortable clothing and plan to rest afterward, as you might feel lightheaded or tired after the needle is inserted.
What Happens During the Test?
A healthcare professional will clean the area on your arm with an antiseptic solution and insert a small needle into a vein. Blood will be gently drawn into a test tube. The process usually takes a few minutes, and you may feel a brief pinch. The blood sample is then sent to a lab for testing.
What Are Possible Results?
Results can vary depending on your health, age, and other factors. Your doctor will compare your TSH level to a reference range specific to your situation and explain what it means for you. High or low TSH levels may signal thyroid dysfunction, which your doctor will discuss with you further.
Reference range
Adult: 0.4-4.0 mIU/LN/A
Take your thyroid medication after the blood draw if applicable. No fasting required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
TSH Level
Frequently asked questions
What Does a High TSH Level Mean?
What Does a Low TSH Level Mean?
What If My TSH Level Is Within Normal Range?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy